THE political pundits analyzing this week's primaries still are wondering whether negative advertising carried Ohio and Texas for Hillary Rodham Clinton.

Hollywood has its own explanation: March 4 was Clinton's personal super Tuesday, because it was the night the stars came out for her as never before.

Over the last week, in fact, both Democratic presidential campaigns have glittered with more wattage than the Las Vegas Strip. Those same pundits all admit that Hollywood is a great place to raise money, but many of them are inclined to question the value of celebrity endorsements. Clearly, the candidates have no such reservations, because when they were playing for big stakes this week they called out to every actor they thought would answer the phone.

Of all the celebrity campaigners, however, the most visible was Jack Nicholson-- and, in typically unconventional fashion, he never left home.

The actor joined up with pal director-activist Rob Reiner (who worked with Jack on his latest movie, "The Bucket List") and several other Hollywood friends to release a YouTube campaign ad for Clinton on Saturday.

The commercial, which set off campaign issues with clips from some of Nicholson's iconic film roles (the Joker from "Batman," the delusional dad in "The Shining," the maniacal Marine Corps colonel in "A Few Good Men"), was an instant YouTube hit. By Wednesday, the ad (in all its bootlegged forms) had rolled up more than 2 million views on the video site.

Nicholson even picked up extra mileage for his candidate by going on MTV News, where he scoffed at the people who criticize celebs for expressing their opinions.

"I wish they'd stop calling us 'Hollywood nitwits,' " he said. "They can't get along without us. We've got our share of nitwits. I've been called a 'woolly headed intellectual,' neither of which is accurate. I only wish I was woolly headed."

Reiner, who spent the weekend campaigning for Clinton in Dallas and then flew to Ohio with her on election night, figured Tuesday was a now-or-never moment for Hillary's Hollywood supporters.

"It was down to the wire," Reiner said in a phone interview. "I agreed with Bill Clintonand [campaign strategist] James Carville that she had to win Ohio and Texas. I also believed if she did win, she would be the nominee. I believe that now."

Reiner has been in Clinton's camp since fall. He hosted a birthday party/fundraiser for the senator at his Brentwood manse in October. And lately he's been busy lobbying those elusive superdelegates on the senator's behalf. Recently, while wrapping up "The Bucket List," Nicholson mentioned to Reiner that he also was supporting the New York senator.

Reiner, who is not the sort of guy to miss an opportunity, immediately went to work figuring out the perfect role for Nicholson, who is anybody's idea of an A-list advocate. "I called the campaign right away and said, 'Jack is a supporter!' " Reiner said. " 'What can we do with him?' "

First, they put him in a radio ad. Then they decided to come up with something grander and hipper -- a viral video of the sort that has changed everybody's idea of what constitutes "free media" in this election cycle.

"Pushing Daisies" producer Bruce Cohen came up with the film-clip concept. He and Reiner teamed with former Clinton White House staffer Chad Griffin and writer-director John Krokidas. Last week they took the final product to Nicholson for a screening.

In political speak, the actor endorsed the message.

Of course, the critics weighed in after the ad's Internet debut. They complained that it was just montage of Nicholson's memorable film moments, including one snippet that shows Nicholson's character in "A Few Good Men" arguing that "there is nothing sexier than saluting a woman in the morning."

One blogger sniffed that, " 'Sexy' is not a presidential criteria." (It is in Hollywood.)

As is typical with YouTube, however, you can gauge the effectiveness of an ad by the number of parodies it spawns. According to that measure, the Nicholson ad was a mega hit.

One guy donned sunglasses, then tried (and failed) to do a Nicholson impersonation in his YouTube posting. "Being a celebrity godsend, I have met every president in the White House since 1971," he begins. Finally, he sums up: "I'm Jack Nicholson, and I approve of being Jack Nicholson." Another spoof, put together by an Obama supporter, shows movie clips of Nicholson reacting with outrage to various negative statements about Clinton. It ends: "Sorry Jack. Vote Obama."

The results in Ohio and Texas may not have answered the old question of whether celebrity endorsements move voters, but you can bet neither the Clinton nor the Obama campaign is going to take the chance that they don't. Voters in Pennsylvania had better prepare for a celebrity onslaught, because over the next six weeks, their state is going to look like a busy backlot at Universal.